Pneumatic sound source



Oct. 4, 1966 J. l. EWING ETAL 3,276,534

PNEUMATIC SOUND SOURCE Filed Dec. 14, 1964 BY 5M i? United States Patent O 3,276,534 PNEUMATIC SOUND SOURCE .lohn l. Ewing, Palisades, and Roger Zaunere, West Nyack,

N.Y., assignors to the United States of America as represented bythe Secretary of the Navy Filed Dec. 14, 1964, Ser. No. 418,360 7 Claims. (Cl. 181-5) This invention relates to a pneumatic sound source and especially to a pneumatic sound source for use in the undersea environment.

During recent years, marine geophysical studies have become oriented strongly in the direction of reflection profiling. The'emphasis on the reilection technique is due in a large part to the development of profiler recorders which display the reflection data in cross sectional form, allowing visual correlation and integration of arrivals. Systems utilizing explosives, high-voltage sparks, explosive gas mixtures and various electro-mechanical transducers have been used successfully as acoustic sources which are necessary for the technique of reflection proling.

Of course, systems using explosives, high-voltage sparks and explosive gas mixtures pose a definite safety hazard. Pneumatic sound sources are safer than these and are simpler and more reliable lthan electromechanical transducers.

The objects and advantages of the present invention are accomplished by the sudden and rapid release of a volume of high-pressure air into a surrounding lluid medium. A typical embodiment of the invention utilizes a piston within a piston cylinder, the piston and cylinder being so constructed as to form three chambers within the cylinder, an upper, `middle `and lower chamber. The lower chamber is connected to an inlet for high-pressure air and a conduit passes from the lower chamber through the interior of the piston to the upper chamber. The upper end of the piston abuts the upper chamber, but the part of the surface area which is in contact with the air in the upper chamber is smaller than the total surface area of the upper end of the piston. Downward movement of the piston under the influence of high-pressure air from the upper chamber eventually exposes the lower chamber to the outside environment, permitting the sudden discharge of the high-pressure air in the lower chamber, and thus the generation of sound.

An object of the present invention is to provide an efficient, safe, reliable and relatively inexpensive pneumatic acoustic source for use in fluid media, such as the oceans.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

The cross-sectional diagram indicates that the device comprises a piston cylinder 12 and a piston 14. The cylinder 12 has a side wall and an upper wall or ceiling, but lacks a bottom wall. The particular cylinder shown has a lower member 16 and an upper member 18, the lower member being threaded into the upper member. The upper surface 119 of the lower cylinder member 16 forms a stop which prevents the piston 14 from being shot out of the cylinder 12 on its downward stroke. The lower end of the cylinder 12 is open and the upper end is closed, the upper end being formed from a relatively thick piece of material.

The excise central space in the cylinder 12 is substantially cylindrically shaped which is also the general shape of the piston cylinder 12. A second smaller, cylindrically shaped, excised space 20 is found in the thick piece of material forming the upper end of the cylinder and is known as the upper chamber. This upper chamber 29 opens upon the central excised space of the cylinder 12.

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A piston 14 is located within the central excised space of the piston cylinder 12. Both the piston and the cylinder may be fabricated from a strong, rigid material such as steel.

The piston 14 has a central shank 22 the upper end of which is formed with a wide flange 24. The upper surface of this flange 24 has a wide outer portion 26 which fits against the upper interior surface 27 of the cylinder 12, and a narrower, raised central portion 28 which fits into and seals off the bore of the upper chamber 2t). A Teflon AO ring 30 is fitted around the periphery of the raised central portion 23 to make the seal tight.

The side of the upper flange 24 abuts against the side interior surface 29 of the cyinder 12 and a tight llt is accomplished here by a neoprene O ring 32. About twothirds of the way down the piston 14, the shank 22 flares out into another flange 34. The side of this middle flange 34 is in contact with the side interior surface 29 of the cylinder 12 and a tight fit is accomplished by a neoprene O ring 36 and a Teflon back-up ring 37.

The shank 22 of the piston 14 flares out once more at its lower end to form a piston head 38 the sides of which contact the side interior surface 29 of the cylinder 12. A tight fit is accomplished here by a fourth O ring 40.

The upper flange 24, the shank 22 of the piston, the middle flange 34 and the side wall of the cylinder 12 form a chamber within the cylinder which is called the middle chamber 42. The middle flange 34, the lower part of the shank, the piston head 38 and the side wall of the cylinder form lanother chamber within the cylinder which is called the lower chamber 44.

A narrow passageway or conduit 46 is drilled through the piston 14 to connect the lower and the upper chambers 44 and 20. An inlet port, called the low-pressure port 48 because it is connected to a source of low-pressure air, is drilled through the cylinder wall and couples with the middle chamber 42. A second inlet port, called the highpressure port 50 because it is connected to a source of high-pressure air, is drilled through the cylinder wall and couples with the lower chamber 44. A third port called the exhaust port 52 is drilled through the `cylinder wall on a line with the interior surface of the upper wall of the cylinder 12.

In opera-tion, the low-pressure port 48 and the highpressure port 5G are coupled to sources of low-pressure air and high-pressure air, respectively, and the device is lowered into the ocean. Low-pressure air is introduced into the middle chamber 42 raising the piston 14 to its topmost position (the upper end of its stroke) in which the upper surface 26 or the upper flange 24 is in close contact with the upper interior surface 27 of the cylinder. High-pres sure air is then introduced into the lower chamber 50, filling it and the upper chamber 20 because lthey .are connected by the conduit 46.

An upward force is exerted on the piston 14 by the lowpressure air in the middle chamber 42 and a downward force is exerted on the piston 14 by the high-pressure air in the upper chamber 2t). At the start, the force exerted by the low-pressure air is greater because it is exerted against a greater area. However, as the pressure in the upper chamber increases, the downward force reaches a point at which it starts Ito move the piston down slowly. Finally, the piston moves down far enough so that the raised central portion 28 of the upper flange 24 of the piston 14 no longer seals off the upper chamber 20. At this point, the upper chamber 20 connects with a space which has been formed between the upper interior surface 27 of the cylinder and the upper surface 26 of the upper piston flange 24. This places high-pressure air over the wide area of the upper flange and provides a downward force-which is much greater than the upward force devel 3 oped by the low-pressure air which is in contact with a smaller area of the upper flange.

The sudden increase lin downward pressure when the seal of the upper chamber 20 is .broken results in a very sudden, violent downward stroke of the piston 14, moving the piston head 38 past the lower end of the cylinder wall 16 and exposing the lower chamber 44 to the outside environment. All the air in the lower chamber is explosively released into the sea water and the shock develops a pulse-like acoustic wave which moves through the water. At the same time, the high-pressure air in the upper charnber 20 is released through the exhaust outlet 52 and the device is ready for another cycle.

The spacings between the three flanges 24, 34 and 28 and the stop 19 are such that when the upper flange 24 abuts the stop 19, the lower chamber 44 is completely past the lower edge of the cylinder wall. Complete and rapid exposure of the lower chamber opening to the outside environment results in the fastest possible rate of discharge of the air contained therein, and therefore a sharp pulse. Of course, in practice, the presence of the shoulder narrows the lower section of the middle chamber so that the downward stroke of the piston compresses the air in the middle chamber, thereby halting the piston before it hits the shoulder.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

We claim: 1. A pneumatic sound source comprising: housing means comprising a substantially longitudinal structure open at one of its longitudinal-axis ends and having an excised central chamber enclosed by a wall and a ceiling opposite the open end,

said structure being formed with a second chamber in said ceiling, said two chambers coupling with each other, and the transverse cross-sectional area of said second chamber being less than that of said central chamber,

said structure also being formed with an upper, a

lower and a middle port in said wall; piston means located within said central chamber and comprising a central shank bearing three encircling flanges, an upper flange at one end, a lower flange at the other end, and a middle flange between the other two, l the sides of said flanges bearing against said housingmeans wall to form a lower chamber and a middle chamber which is intermediate said lower chamber land said second chamber, the surface of said upper flange sealing off said second chamber in a fluid-tight manner when said surface is pressed against the internal surface of said ceiling,

said central shank 'being formed with a conduit therein coupling said lower chamber with said second chamber,

said upper port being located close to the internal surface of said ceiling, said middle port coupling with said middle chamber and said lower port coupling with said lower chamber; and

sealing means for sealing said chambers against the passage of fluid therebetween,

said sealing means permitting said piston means to slide within said housing means, so that said lower chamber is completely sealed from the outside environment when said upper flange is pressed :against said ceiling and is exposed to the outside environment when said piston means is moved downwards.

2. A pneumatic acoustic source comprising:

a piston cylinder comprising a cylindrical side wall and a ceiling which form a central excised space open at its lower end,

4 said ceiling being formed with an excised space therein connecting with said central excised space but not extending completely through said ceiling, the transverse cross-sectional area of the ceiling excised space being smaller than the transverse cross-sectional area of said central excised space, said side wall being formed with an upper, a middle and a lower port therethrough, the upper port being located just beneath the ceiling of said cylinder;

a piston formed with a central shank, an upper flange,

a middle flange and a lower flange, said flanges and cylinder side wall forming a middle chamber between said upper and middle flanges and a lower chamber between said middle and lower flanges, said middle chamber being coupled with said middle port and said lower chamber being coupled with said lower port,

said piston also being formed with a conduit extending from said lower chamber to said ceiling excised space for coupling therebetween; and means afllxed to the side walls of said flanges and the upper surface of said upper flange for making fluidtight contact with the interior surface of said cylinder, said ceiling excised space and said lower and middle chambers being completely sealed from each other except for said conduit through said piston shank,

said piston being forced upward into contact with the ceiling of said cylinder when low-pressure fluid is admitted to said lower chamber and said ceiling excised space, and being forced quickly downward when the downward movement of said upper flange unseals said upper chamber and couples it to said central excised space, said quick downward movement of said piston acting to expose said lower chamber to the outside environment thereby allowing quick discharge of the high-pressure fluid contained therein.

3. A device as set forth in claim 2, including an internally extending stop on the inner surface of the side wall of said cylinder, said stop being located at such a position that downward movement of said piston completely exposes said lower chamber to the outside environment, said stop preventing said piston from completely Ileaving said central excised space of said cylinder.

4. A pneumatic acoustic source comprising:

a piston cylinder comprising a cylindrical side wall and a ceiling which form a central excised space open at its lower end,

said ceiling being formed with an excised space therein connecting with said central excised space but not extending completely through said ceiling, the transverse cross-sectional area of the ceiling excised space being smaller than the transverse cross-sectional area of said central excised space,

said side wall being formed with an upper, a middle and a lower port therethrough, -the upper port being located just beneath the ceiling of said cylinder;

a piston formed with a central shank, an upper flange, a middle flange and a lower flange, said flanges and cylinder side wall forming a middle chamber between said upper and middle flanges and a lower chamber between said middle and lower flanges, said middle chamber being coupled with said middle port and said lower chamber -being coupled with said lower port,

said piston also being formed with a raised portion extending upwards from the center of said upper flange into said ceiling excised space to form an upper chamber,

`said piston also being formed with a conduit extending from said lower chamber to said upper chamber; and

means affixed to the side walls of said flanges and said raised portion of said upper flange for making fluidtight contact with the interior of said cylinder,

said piston being forced upward into contact with the ceiling of said cylinder when low-pressure fluid is ladmitted to said middle chamber, and being forced slowly downward when high-pressure iluid is ad mitted to said lower chamber and said upper chamber, and being forced quickly downward when the downward movement of said raised portion of said upper ange unseals said upper chamber and couples it to said central excised space, said quick downward movement of said piston acting to expose said lower chamber .to the outside environment thereby allowing quick discharge of the high-pressure fluid contained therein.

S. A device as set forth in claim 4, including an internally extending stop on the inner surface of the side wall of said cylinder, saidrstop being located,V at such a position that downward movement of said piston completely exposes said lower chamber to the outside environment,

said stop preventing said piston from completely leaving said central excised space of said cylinder.

6. A lpneumatic acoustic source comprising:

a piston cylinder formed of an upper and a lower section `which comprise the boundaries of a central ex- -cised space, said upper section formed with a cylindrical side wall internally threaded at its lower end and a ceiling closing off the cylindrical side wall at its upper end, said lower section comprising a tube externally threaded at its upper end, said lower section being threaded into said upper section to form a s ingle side wall closed at one end and open at its other end and having an internal shoulder formed by the threaded end of said lower section,

said ceiling being formed with an excised space therein connecting with said central excised space but not extending completely through said ceiling, the transverse cross-sectional area of the ceiling excised space being smaller than the transverse cross-sectional area of said central excised space,

said side wall being formed with an upper, a middle and a lower port therethrough, the upper port being ilocated just beneath the ceiling of said cylinder;

a piston formed with a central shank, an upper flange, la middle flange and a lower flange, said flanges and cylinder side wall forming a middle chamber between said upper and middle anges and a lower chamber between said middle and lower anges, said middle chamber Ibeing coupled with said middle port and said lower chamber being coupled with said lower 'ports said piston also being formed with a raised portion extending upwards from the center of said upper lange into said ceiling excised space to form an upper lchamber, said piston also being formed with a conduit extending from said lower chamber to said upper chamber; and

means aixed -to the side walls of said tlanges and said raised portion of said upper ange for making fluidtight sliding contact with the interior surface of said cylinder,

said piston being forced upward into contact with the Y ceiling of saidV cylinder when low-pressure fluid is admitted to said middle chamber, being forced slowly downward when high-pressure fluid is admitted to said lower chamber and said upper chamber, and being forced quickly downward when the downward movement of said raised portion of said upper flange unseals said upper chamber and couples it to said central excised space, said quick downward movement of said piston acting to expose said lower chamber to the outside environment thereby allowing quick discharge of the high-pressure uid contained therein.

7. A device as set forth in claim 6, wherein the lengths of the side wall of said cylinder between said ceiling and said internal shoulder, and between said internal shoulder and the open end of said cylinder, are such that said lower chamber is completely closed when said piston is moved up to Icontact said ceiling and said lower chamber is substantially completely exposed to the outside environment when downward movement of said piston places said upper flange in contact with said internal shoulder.

References Cited by the Examiner UNITED STATES PATENTS 3,077,944 2/1963 Padberg 181-.5 3,099,813 7/1963 Anderson 181-.5 3,111,898 11/1963 Foster 102-25 BENJAMIN A. BORCHELT, Primary Examiner. W. KU] AWA, Assistant Exdmner. 

1. A PNEUMATIC SOUND SOURCE COMPRISING: HOUSING MEANS COMPRISING A SUBSTANTIALLY LONGITUDINAL STRUCTURE OPEN AT ONE OF ITS LONGITUDINAL-AXIS ENDS AND HAVING AN EXCISED CENTRAL CHAMBER ENCLOSED BY A WALL AND A CEILING OPPOSITE THE OPEN END, SAID STRUCTURE BEING FORMED WITH A SECOND CHAMBER ENCLOSED SAID CEILING, SAID TWO CHAMBERS COUPLING WITH EACH OTHER, AND THE TRANSVERSE CROSS-SECTIONAL AREA OF SAID SECOND CHAMBER BEING LESS THAN THAT OF SAID CENTRAL CHAMBER, SAID STRUCTURE ALSO BEING FORMED WITH AN UPPER, A LOWER AND A MIDDLE PORT IN SAID WALL; PISTON MEANS LOCATED WITHIN SAID CENTRAL CHAMBER AND COMPRISING A CENTRAL SHANK BEARING THREE ENCIRCLING FLANGES, AN UPPER FLANGE AT ONE END, A LOWER FLANGE AT THE OTHER END, AND A MIDDLE FLANGE BETWEEN THE OTHER TWO, THE SIDES OF SAID FLANGES BEARING AGAINST SAID HOUSING MEANS WALL TO FORM A LOWER CHAMBER AND A MIDDLE CHAMBER WHICH IS INTERMEDIATE SAID LOWER CHAMBER AND SAIDS SECOND CHAMBER, THE SURFACE OF SAID UPPER FLANGE SEALING OFF SAID SECOND CHAMBER IN A FLUID-TIGHT MANNER WHEN SAID SURFACE IS PRESSED AGAINST THE INTERNAL SURFACE OF SAID CEILING, SAID CENTRAL SHANK BEING FORMED WITH A CONDUIT THEREIN COUPLING SAID LOWER CHAMBER WITH SAID SECOND CHAMBER, SAID UPPER PORT BEING LOCATED CLOSE TO THE INTERNAL SURFACE OF SAID CEILING, SAID MIDDLE PORT COUPLING WITH SAID MIDDLE CHAMBER AND SAID LOWER PORT COUPLING WITH SAID LOWER CHAMBER; AND SEALING MEANS FOR SEALING SAID CHAMBERS AGAINST THE PASSAGE OF FLUID THEREBETWEEN, SAID SEALING MEANS PERMITTING SAID PISTON MEANS TO SLIDE WITHIN SAID HOUSING MEANS, SO THAT SAID LOWER CHAMBER IS COMPLETELY SEALED FROM THE OUTSIDE ENVIRONMENT WHEN SAID UPPER FLANGE IS PRESSED AGAINST SAID CEILING AND IS EXPOSED TO THE OUTSIDE ENVIRONMENT WHEN SAID PISTON MEANS IS MOVED DOWNWARDS. 